Tried to reply to that earlier, but you were locked.
I think your instincts are right. If it was important, she would have left a message or called back. You could always shoot a text (now that some time has passed) that says something like: "Hey! Just noticed you called. Let me know if you need me." That way, you're acknowledging her attempt at contact but doing it in a way that is detached (you're not calling her OR asking her an open-ended question that may appear as though you are trying to engage her in conversation. It's amazing what the WAS looks at as "pressure.") But I think you're also fine leaving it alone.
M: 40 H: 44 Married 14 years S11 & D6; D20 & D19 from previous M 2BDs/PAs, 8 years apart Piecing: April 2014